Effects of alcohol septal ablation on coronary microvascular function and myocardial energetics in hypertrophic obstructive cardiomyopathy

Timmer SA, Knaapen P, Germans T, Dijkmans PA, Lubberink M, ten Berg JM, ten Cate FJ, Russel IK, Gotte MJ, Lammertsma AA, van Rossum AC. Effects of alcohol septal ablation on coronary microvascular function and myocardial energetics in hypertrophic obstructive cardiomyopathy. Am J Physiol Heart Circ Physiol 301: H129-H137, 2011. First published February 18, 2011; doi:10.1152/ajpheart.00077.2011.-This study investigated the effects of alcohol septal ablation (ASA) on microcirculatory function and myocardial energetics in patients with hypertrophic cardiomyopathy (HCM) and left ventricular outflow tract (LVOT) obstruction. In 15 HCM patients who underwent ASA, echocardiography was performed before and 6 mo after the procedure to assess the LVOT gradient (LVOTG). Additionally, [(15)O] water PET was performed to obtain resting myocardial blood flow (MBF) and coronary vasodilator reserve (CVR). Changes in LV mass (LVM) and volumes were assessed by cardiovascular magnetic resonance imaging. Myocardial oxygen consumption (M(V) over dotO(2)) was evaluated by [(11)C] acetate PET in a subset of seven patients to calculate myocardial external efficiency (MEE). After ASA, peak LVOTG decreased from 41 +/- 32 to 23 +/- 19 mmHg (P = 0.04), as well as LVM (215 +/- 74 to 169 +/- 63 g; P < 0.001). MBF remained unchanged (0.94 +/- 0.23 to 0.98 +/- 0.15 ml.min(-1).g(-1); P = 0.45), whereas CVR increased (2.55 +/- 1.23 to 3.05 +/- 1.24; P = 0.05). Preoperatively, the endo-to-epicardial MBF ratio was lower during hyperemia compared with rest (0.80 +/- 0.18 vs. 1.18 +/- 0.15; P < 0.001). After ASA, the endo-to-epicardial hyperemic (h)MBF ratio increased to 1.03 +/- 0.26 (P = 0.02). Delta CVR was correlated to Delta LVOTG (r = -0.82; P < 0.001) and Delta LVM (r = -0.54; P = 0.04). MEE increased from 15 +/- 6 to 20 +/- 9% (P = 0.04). Coronary microvascular dysfunction in obstructive HCM is at least in part reversible by relief of LVOT obstruction. After ASA, hMBF and CVR increased predominantly in the subendocardium. The improvement in CVR was closely correlated to the absolute reduction in peak LVOTG, suggesting a pronounced effect of LV loading conditions on microvascular function of the subendocardium. Furthermore, ASA has favorable effects on myocardial energetics.